High-voltage evacuated acceleration tube for increasing the total voltage and voltage gradient thereof



J. G. TRUMP ET AL 2,521,426 HIGH-VOLTAGE EVACUATED ACCELERATION TUBE FOR INCREASING Sept. 5, 1950 THE TOTAL VOLTAGE AND VOLTAGE GRADIENT THEREOF 2 Sheets-Sheet 1 Filed March 16, 1949 Sept. 5, 1950 J. G. TRUMP ET AL 2,521,426

HIGH-VOLTAGE EVACUATED ACCELERATION TUBE FOR INCREASING THE TOTAL VOLTAGE AND VOLTAGE GRADIENT THEREOF 7 Filed March 16, 1949 2 Sheets-Sheet 2 Patented Sept. 5, 1 950 HIGH-VOLTAGE EVACUATED ACCELERA- TION TUBE FOR INCREASING THE TOTAL VOLTAGE AND VOLTAGE GRADI- ENT THEREOF John G. Trump, Winchester, and Robert W. Cloud, Lexington, Mass, assignors to Research Corporation, New York, N. Y., a corporation of New York Application March 16, 1949, Serial No. 81,648

12 Claims. (Cl. 250-275) This invention particularly relates to evacuated, high-voltage, acceleration tubes of unusual voltage strength and compactness, for the purpose of increasing the total voltage and the voltage gradient that can be applied thereo.

In order that the broad principle of the invention may be readily understood, we have in the accompanying drawings disclosed several embodiments or representations of a structure or apparatus indicative of the invention and by which the invention may be practiced, and we shall in the ensuing specification describe merely such preferred embodiments of the novelv acceleration tube, without limiting ourselves to such type of tube, nor merely to the disclosed e2nbodiments thereof. We shall also herein set forth, but Without limiting ourselves thereto, the best ways known to us for practicing our invention.

In the United States patent to Trump and Cloud, No. 2,460,201, dated January 25, 1949, there is disclosed an acceleration tube, or type of electronic tube, comprising or including a series of metallic disk or diaphragm electrodes alternating with annular members of glass or other suitable insulating material.

The acceleration tube here-.

in disclosed is or may be of the same general construction as that shown in the said patent, and preferably, as disclosed and claimed in such patent, We join the metallic disk or diaphragm el =ctrodes and the alternating insulating annular members with thermo-plastic or thermo-setting film, which film constitutes the vacuum-sealing and mechanical bond between such insulating annular members of glass or other suitable insulating material, and the said alternating metalenvelope of the high-voltage accelerating tube or othertype of electronic tube is composed and which is provided with suitable cathode and anode assemblies.

7 Our present invention is, however, not concerned particularly with or limited to the manner or means for joining the metallic electrodes and the insulating annular members to constitute the envelope of the tube, but is concerned with means for increasing the total voltage which can 1 he electrode disks or diaphragms of which the in 1895 there have been persistent efforts to increase the voltage which could be applied to acceleration tubes. The eiifect of higher voltages is to increase the penetrating power and intensity of the radiation. X-rays produced by several million volts are more suitable for the irradiation of deep tumors in cancer therapy and are capable of quick radiographic examination of heavy metal sections. Such high-voltage acceleration tubes are needed also for the acceleration of electrons and positive ions in a variety of pure and applied research undertakings, including the investigation of the structure of the atomic nucleus.

Multi-stage acceleration tubes capable of operating with voltage gradients of one-million volts per foot of column have been successfully built for two-million volt operation. These voltage gradients along the column of an evacuated tube accelerating substantial electron or positive-ion currents are far in excess of those thus far common to the art.

The results thus far accomplished have required very extended and long continued research on the mechanism of voltage insulation in high vacuum, on the electrical and mechanical properties of materials used in acceleration tubes, and on the design and technique of fabrication, and respecting the performance of such tubes. Such extended and lengthy research has resulted in important improvements for which applications are now pending in the United States Patent Of= fice in the names of ourselves or of one of us, as well as in the said Patent No. 2,460,201, issued to ourselves, and also in an application of Dr. Van de Graaif and Dr. Buechner with whom we have been associated in the researches referred to.

One of the limitations in the application of voltage to an acceleration tube is reached when high electron currents are developed spontaneously within the tube. These currents often take the form of transients, sometimes referred to as dark currents, and our researches have led us to believe that they are due to the multi plication of some initial electrons by a series of collisions with the successive metallic disk or diaphragm electrodes of the acceleration tube, including the end electrodes thereof. We have, as the result of our researches, concluded that secondary emission and high-field electron emission characteristics of the I electrode surfaces within the tube play an important role in determining the voltage at which such transients or dark currents appear as well as the severity thereof.

Our researches in this connection have also series of metallic electrode disks or diaphragms spaced apart by the alternating inSulating ahnular members of glass, porcelainorthe-like. Such metallic electrodes performthefunction of accelerating and focusing, and have the advantage that the electric gradient; on .the metal surface thereof is kept at a rninimunr The said disk or diaphragm electrodes: been constructed as rings or annuli; that is to say, they have been provided with an axialhole therethrough, and, as disclosed, for example, in our said Patent No. 2,460,201, the saidaxial holes have all been of the same shape and area. Such metallic electrodes have been, identical with each other in shape and size throughout :the length of the acceleration tube, and the in- --sulating annular members of-glass, porcelainor thelike have also been identical with each other. Thesaid electrode disks or diaphragms have been thin and the annular insulation members have been of relatively larger. thickness so that next adjacent metallic electrode disks'or diaphragms have been separated from eachiother in the preferred construction by a substantial -part of an inch or even more in :tubes of larger diameter. The outer edges of 'the metallic electrode disks or diaphragms and the annular insulation members have'been substantially coterminous, but the inner edges ofthe metallic electrode disks or diaphragms have extended inward -bey'ondthe inner edges of saidannular members substantially to the extent indicated in our Patent No. 2,460,201 andprovide shielding as explained in said patent and in our co-pending applications. 1?

While our present invention is not limited in its application to acceleration tubessuchasthat justdescribed, the principle ofourpresent injvention will be apparent upon a consideration of the characteristics of such-acceleration tubes, taken with the novel features of our invention now to be set forth. s V j l As a result of our said researchesand investigations, we have discovered that by progressively or otherwise varying the diameter of the axial holes in the different metallic electrode disks or diaphragms of the tube with relation to each other, we thereby reduce the tendency of an initial charged particle to multiply "itself many times over en route from thecathode of the acceleration tube to the anode thereof bywthe release of secondary electrons, photonsand positive ions. y Such multiplication ofan initial; charged particle is an exponential process similar to that encountered in the well known multiplier.tube=" A typical high-voltage acceleration tube may-be regarded as a multiplier tube" with an extraordinarily large number of electrodes andtherefore could be particularly effective in. the development of unwanted transient currents-of very high peak values, and this our researches and experiments have shown tobejthefcase. Instead of having the metallic-electrode disks or diaphragms all provided with the same size and area of axial hole therethrough, we progressively or otherwise change the diameters and areas .of the said axial holes of the metallicelechave t trode disks or diaphragms, and therefore avoid to a large extent the possibility of an initial electron multiplying itself through successive collisions with interveningmetallic electrode disks or diaphragms while 'en route from the cathode to or toward the anode of the acceleration tube. This construction and manner of operation We have discovered to be also effective in avoid- ;ing such multiplication of positive ions which tric field toward the cathode, and should they impinge'upon a metallic disk or electrode, they too will cause the secondary emission of elec- ;tro ns which are then accelerated toward the anode end of the tube.

anode, 11i certain cases we have secured the desired effect by progressively increasing the diameters of the said axial holes from the smallest value at the cathode end to the largest value at the In other tubes constituting embodiments of our invention, we have started with a fairly, large axial hole, in .the

'- metallic electrode disk or diaphragm nextto the cathode end of the tube and have gradually reduced the diameter and area of the axial holes of successive metallic electrode disks or..dia-

phragms to the smallest value at an electrode disk or diaphragm which lies intermediatebetween the cathode and the anode of the tube and then again progressively increased the diameterand area of such holes tothelargest value at the anode end of the tube. other embodiments of our We also, in invention, have changed the diameters or areas of the axial holes of the metallic electrode disks or diaphragms threeor more electrode disks or diaphragms havinga given diameter of axial hole therethrough :In all ofthe in the-art.t 4Q. .7

:at or near the cathode end of the tube, and

then have made a discreet change by increase or by decrease to -a new diameter in certain succeeding electrode disks or diaphragms of the tube, and so on throughout the tube to or toward the anode end.

" -While we have in preceding paragraphs'referred to several embodiments of our invention,

it is to be understood that we are not limited thereto 'We'have chosen in the drawings to 11- lustrate five different embodiments of our invention and they will be hereinafter specifically referred to. 4

cases indicated, we have found that darkcurrents or transients of the type referred to have been substantially reduced at a given voltage and that the permissible voltage to give satisfactory operation has been significantly increased.

By progressively or otherwise changing, lengthwise the acceleration tube, the geometry of the electrode disks or'diaphragms .with respect to the diameter and area of the axial holes therethrough in accordance with our invention, we reduce the possibility of exponential multiplication ofrandom. and scattered charged particles, and we have found that we have achieved a fundamental change in the high-voltage acceleration tube art, thereby making possible both higher total voltages and higher voltage gradients along the column of the acceleration tube,

.and therebyperform an important function which has not hitherto been realized or achieved Without here setting forth an thegdifierent embodiments of our invention, we have in the detail.

Referring to the drawings:

Fig. 1 isa vertical, longitudinal, central section, with an intermediate part broken away, taken through an acceleration tube embodying our invention, and wherein the axial circular holes through the metallic electrode disks or diaphragms gradually increase in diameter from the I cathode end to the anode end of the tube;

,Fig. 2 is a sectional view similar to Fig. 1,

but disclosing a construction wherein the axial circular holes in the metallic electrode disks or diaphragms gradually decrease in diameter to an electrode disk or diaphragm intermediate the cathode and the anode assemblies, herein about one-quarter way down the tube column, and then gradually increase in diameter to the maximum area at the anode end of the acceleration tube;

Fig. 3 is a sectional view generally similar to Fig. 1, but showing a construction wherein the diameters of the axial circular holes through electrode disks or diaphragms increase in a series of steps, each step including a small number of electrodes having the same diameter of axial holes;

Fig. 4 is a sectional view generally similar to Fig. 2, but showing a construction wherein the axial circular holes through the electrode disks or diaphragms are of the largest diameter at the cathode end of the tube and uniformly decrease in diameter as in Fig. 2, and then increase in steps to the anode end, each such step including several electrode disks or diaphragms having the same diameter of axial circular holes; and

Figs. 5 and 6 are plan views of modified constructions of the metallic electrode disks or diaphragms.

Referring to the drawings illustrating several selected embodiments of the structure or apat I, and an anode assembly indicated generally at 2.

The saidacceleration tube is in practice mounted within a high-voltage generator in such a way that the cathode end is within the highvoltage terminal and the tube columnis within the column of the generator itself.

The cathode assembly is herein shown as comprising a removable cathode head 3 secured by bolts 4 to the body portion 5 of the said cathode assembly, there being a suitable circular gasket 6 between said parts 3 and 5. lated filament lead I is provided, having a suitable filament 8, such as tungsten, which may be such as is disclosed in our said Patent 2,460,201. The anode assembly 2 of suitable construction is provided with an anode target 9 preferably of gold, as disclosed in one of the pending applications hereinbefore referred to.

The column or envelope of the acceleration tube is composed of a multiplicity of alternating glass, porcelain or other annular insulation members I0 and metallic electrode disks or diaphragms II which desirably are bonded together by a plastic film, as fully disclosed and claimed in our said Patent 2,460,201, but which film is not indicated in the drawings because of draft- A suitable insu- .1

. ing space'limitations. I The said. annular insula- ,.tionmembers Ill andthe metallic electrode disks 2 or diaphragms 'I I' lie accurately placed in planes I perpendicular to the axis of the acceleration tube and are placed at equal distances apart. Forexample, the said electrode disks or diaphragms II are desirably placed one-third of an inch apart. The insulating column of. the acceleration tube is shown as transversely broken away, because of drafting space limitations.

While. our invention is in no wise limited to the disclosed size and relative proportion of parts,

. or the number of annular insulation members and 'electrode disks or diaphragms, the insulating column of the acceleration tube shown in Fig. 1,

is in the present instance, in'practice, twentyfour inches long, and includes thirty-four annular insulation members or rings I0, there being such'an insulation member or ring I0 next to the cathode assembly I and another next to the anode assembly, both desirably bonded'to said assemblies respectively, as in our said Patent 2,460,201.

I There are, in practice, in the acceleration tube represented in Fig. 1, thirty-three metallic elec trode disks or diaphragms II respectively alternating throughout the said acceleration tube with the annular insulation members II]. The outer edges of the 'said annular insulation members I0 and of the metallic electrode disks or diaphragms I I are substantially, though not exactly, coterminous, and in the example of the invention represented in Fig. 1, the column or envelope of the acceleration tube has an extreme outside diameter of four and a half inches.

The diameter of the axial holes through the annular insulation members or rings In is uniform throughout the tube and is such that the internal diameter of the insulating column at the inner wall at said annular insulation members I0 is three inches. Each annular insulation member I0 is nearly three-quarters of an inch thick in said disclosed embodiment of the invention.

We have referred to the outer edges of the annular insulation members I 0 and the metallic electrode disks or diaphragms I I as substantially coterminous. Actually the outside diameter of the said electrode disks or diaphragms II is, in the disclosure referred to, four and threequarters inches as compared with the said four and one-half inch outside diameter of the annular insulation members I0, and each of said electrode'disks or diaphragms II has a thickness of .050 of an inch.

Each of the said metallic electrode disks or diaphragms II is provided with an axial hole therethrough, to which the numeral I2 is generally applied. As already stated, in prior constructions the'axial holes of the entire series of electrode disks or diaphragms were of the same diameter and area.

For the reasons hereinbefore stated (that is, for the purpose of increasing the total voltage that can beapplied to the acceleration tube for the acceleration of particles to high energies, and for the purpose of increasing the voltage gradient vwhich can be applied along the column of the tube for the progressive acceleration of charged particles to high energies), the electrode disks or diaphragms II are, in accordance with our present. invention, arranged with progressively varying internal geometry.

In Fig. 1, the axial circular holes I2 progressively increase in size from a smallest value eagazrgaae 57 at the'fcathode pnd oi' the accelerationtuberto :a larger value'at'fopneari'theanbde.end thereof. I In'the construction shown in Eigshithehiaineter ofthe axial circularholetxl 2. in the topfiiostelectrode disk or diaphragm isjthree,-quarters' ofisan inch, and, the size of said axial holes flagradually and uniformly increasesi throughout thez entire series of electrode disks .orItdiaphra'gms to':a:di-

ameterof the circularaxial hole -.of theaelectrolde disk or diaphragm nearest theia'node enda'oftwo inches. Other dimensions 2 maybe usedi: within the scope and purpose of our einventiongasnthe important feature is that-the inner: edgesiof the metallic disks or diaphragmsqdoenot lieiexactly one over the other, but. progressively extend further inward or outwardpand'ethisrisxalsoitrue of .the other embodiments ofour inventioniherein -disclosed. i z Another embodiment of the; inventionais represented in Fig. 2, 'whereinthestructure the same as in Fig. 1, excepting withjrespect to ,the diameters of theaxial circularholes IZJthrough the respective electrode disks or diaphragmsrll ofsaidFig.2. V j

In the structure shown in Fig. 2, the axial circular hole l2 through thetopmost electrode disk or diaphragm II istwo inches, and-infsuccessive electrode disks-or diap l'fi ms: I l:- ;the Si e oft the -.axial holes [2 thereof rg-r-adua-llw decreases to --three-quarters of an inch in diameter at the eighth electrode disk -or diaphragm from.-the -cathode end of the tube, and-.from there on to -the anode end ofthe tubegthe diameter'of the axial circular holes it gradually .-increases,to two inches.- Thus in Fig. ;2 theidiametergloi thfiaxial circular holes gradually decreasestma pointsub- .stantially one-quarter .01 4 the. distance between r the cathode. assemblyiand A the anode assembly and from there on-- gradually: increases; ,-j ,ust ,above, stated. -Weware snot, however, limited to v this-location of smallest axialppening. g 7' "I: The construction showning-Fig. in all ;refi s r o -t tsh n ini s; l'; exc p with'respect to the diameter of the axialxicircular holes-JZ. through the electrode-disks ordiamh a H In the. qe rus ie s s wn inEi a the diam Qis h a ac cu' ri- .heles l v rlQ= n:-discrcc eps. nd n he. qnst1:uctic .shown in said Fig; 3 each of the said St ps-ine u e th e -i s .Q q a h ssma tbeaii met of whose axial; circular holes l2 is'thesame. "T i h m ment ti he nv nt on shown -F 3, there are 'el rsst n ea hhavinsthr suciccssi ve electrode disks pr diaphragms ll and, as stated, the diameter of the axialioilfcu ar holes 4 of s c ele r e-d sks Q :d ph a s is least in the firststepof three-such disksjolfidia- ..phragms all haying the same diameter o axial circular hole 12, is. very slightly greaterinfthe nextstep of three disks orudiaphragms''l l -'.all having :axial circular yholes, I2. ofulsuch' slightly larger diameter, and so on ,throug-hout alli the eleven or other number of steps. (eleven such steps beingindicatedgini Fig. 3); the diameter. of 1 1 axial holes -l2;thr0'1Igh the electrode disks or diaphra ms. of each such ste being very-slightly greater. than in the-next precedingstep... In the e mbodiment.;of the 'inventionshow'n' in :IEig.--4, the constructionis' the same as in Fig. 2, excepting with, respect to the. diameter of the axial circular holes J 25 of the disks on .diaphragms li lngrthe construction. ShOWnL-iILFig l,:..t,he-*diameter of the axial circular,holes '-J.2 gradually .and uniformly decreasesithough ithejidecrease 111 213? be -.,in :stepsasi imiigmm sfmm the :largest.

diame'ter' or two inches of the topmostfelectiode 1 disk: ordiaphragml t-nearest the cathode assembly to the eighth disk or.,diaphragm l I from said electrode assembly and then-the diameter of the axial circular holes 12 from there on to the anode end of the tube increases in steps, each-stepmeluding threeorfour disks or diaphragms II, and

all the'disks or diaphragms H of each step-have the same diameter of axial circular holes l2 among themselves, but the diameters of said axial circular holes l2- slightlyincrease in each succeeding step orgroup to the maximum diameter of two inches atthe anode end of the acceleration tube; We are not, however, limited to this location of smallest axial opening.

' a With respect to theconstruction shownin Figs. 2 and 4 wherein, through a portion of the tube extending from .the cathode end, the diameters and areas of the axial holesin the metallic electrodes decrease instead of increasingfit will be observed that in such constructions the inner edges of the metallic disks or diaphragm's do not he directly one over another, but terminate at I differentdistances from the'axial' center Of the i have reduced opportunity for producingsecondary electronsby impact, and moreover anyelectrons originating in the referred to portion of the tube'would tend to be collected by the succeeding disks or diaphragms in that'portion of thetube, since such metallic disks or diaphragms progres- .sively jut out more and more toward the axial center of thetube.

Although we have herein given precise dimensions of parts, our invention is'not'limited there- .to, and in-=other embodiments 'of the invention other dimensionsr'of'the parts maybe employed within-the scope of theinvention.

. -In:those embodiments of ourinvention thus far-specificallydescribed, each of the electrode disks ordiaphragms is provided with an axial ofthe electrode disks or dia hragms, especiallyhole only, theseholes' varying in area or diameter as hereinbefore described. In the case'of certain thosein whichthe axialqholes areof the least area or diameter, and-where the tube is intended forthe: acceleration of positive ions; the reduction of the area-of axial holes does'or may cut portantconsideration, Therefore; 'in, those dia- ,phrams wherethe area of the-axial holeisactu- ,ally rather small, we provide oneor. more additional small holes to assistjini maintaining pump- .ing, speed, Such additional hole or holes, how- Fig. 5 we'have represented in eyer,;has on have little eifect on the operation'of the diaphragm V or diaphragms assari electrostatic lens.

planview one of the electrodedi'sks or dia'phragms H, such as adiaphragm represented iniFigJ2 as having an axial hole' having a diameterof three-quarters of..'an inch; In such an electrode, and if desire'd ain acnumb'er of r the diaphragms of smallest -di- "ameter, we provide one or more additionalsrnall thrdwg'h-holes=:l3. In said figure, two "such' additional small holes are. provided at opposite sides: of the axial hole l2.. We may provide one or.

more than two of the additionalsmall holes and position them at .any desired point.

In Figs. 1 to 4, the axial holes are all centrally and concentrically positioned and differas.

described in diameter or area. While we prefer the. constructions shown in Figs. 1 to 4, we may make the axial holes in the disks or diaphragms all of the same size or substantially the same size, but position them eccentrically with respect to the actual center of the said disks or diaphragms, We may varysuch eccentricity by progressively,

advancing ,circumferentially in successive diaphragms or groups of diaphragms. say, we. change the orientation slightly of these holes. Wemay alternately advance and retard such eccentricity insuccessive diaphragms. The purpose of such construction is to trap sooner or later the. non-axial charged particles, "while the axial particles are focused and accelerated.

In Fig. 6 wehave represented two diaphragm ure. makesit..evident that the eccentricity is slightly circumferentially advanced in the low er diaphragm with respect to the upper diaphragm. That is, the orientation is slightly changed. As stated,-such-variation of the eccentricit -may be clockwise or contraclockwise.

Our invention comprehends increasing the voltage gradient which can be applied to an evaculated m ultiple-electrode tube for the acceleration of charged particles. to high energiesand of reducing stray currents in such a tube by markedly reducing the tendency for multiplication of stray charged particlesbecause of secondary emission b collision with successive'elec trode diaphragm, We do this byiproviding "a progressive variance with respect to each other of the holesin the electrodes through which'the particles pass; Such,,progressive variance of the holes in the electrodediaphragms may be in size,

shape or orientation. ,Respecting those formsof the invention wherein the diameters or areas of the axial openings through the metallic electrodedisks decrease from the cathode end of the tube onward, as in Figs. 2 and 4, our invention is not limited to constructions wherein the smallest axial opening is at any particular point intermediate the cathode and the anode, the invention being of broad scope in this respect. We believe, however, that for both electron and positive-ion acceleration tubes, the most constricted region should be kept nearer to the cathode end of the tube, but the scope of our invention is not to be so defined.

Having thus described several embodiments of the invention, it is be understood that although specific terms are employed, they are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth in the following claims.

We claim:

1. An evacuated high voltage acceleration tube for increasing the voltage and voltage gradient which can be applied along the insulating envelope thereof in effecting the progressive acceleration of charged particles to high energies and for reducing the tendency to or opportunity That is to for producing secondaryparticles such as electrons, positive ions and photons in said tube, com-. prising a multiplicityofmetallic ring-like,elec-. i trode members and alternating insulating ringlike members only, bondedtogether in face-toe face relation to constitute -the; insulating enve-.

lope thereof, and having at its respective ends cathodeand anode assemblies, the areas or cli-. ameters of the axial holes of thesaid metallic. electrode members of said. tube varying among themselves.

2. .Annevacuated high voltage acceleration. tube in accordance with claim -l,.wherein the said .variation of the areas or diameters of the axial holes of the metallic electrode members is a progressive increase from a smallest valuesubstantially at the cathode end of the tube to a larger.

value toward the anode end thereof.

3.. .An evacuated high-voltage acceleration tube-- in accordance with claim 1,'wherein the said-variation of the areas or diameters of the axial holes of the metallic electrode membersis a--progressiveincrease by groups of said metallic electrodes from a smallest value substantially at the cathode end of the tube to a larger Value towar the anode end thereof.

4. An evacuated high-voltage acceleration tubein accordance with claim 1, wherein the said .variation ofthe areasor diameters of the axial holes of the metallic electrode members is a pro-' gressive decrease from a smallest, value substanf.

tially at the cathode end of the tube toward th anode end thereof.

to the anode end.

6. An evacuated high-voltage acceleration tube in accordance with claim l, wherein'the, said variation of the areas ordiameters of the axial holes of ]the;metallic electrodemembers constitutes an eccentric variation in a circumferential direction of; the position of the said axial holes of said metallic electrode members with respect 1 to the longitudinal axis of the said acceleration tube.

7. An evacuated high-voltage acceleration tube for increasing the voltage and voltage gradient which can be applied along the insulating envelope thereof in effecting the progressive acceleration of charged particles to high energies and for reducing the tendency to or opportunity for producing secondary particles such as electrons, positive ions and photons in said tube, comprising a multiplicity of metallic ring-like electrode members and alternating insulating ring-like members only, bonded together in face-to-face relation to constitute the insulating envelope thereof, and having at its respective ends cathode and anode assemblies, the areas or diameters of the axial holes of the said metallic electrode members of said tube varying among themselves, at least one of the metallic electrode members having substantially a smallest axial opening therein, being provided with at least one additional small through-hole to assist in maintaining pumping speed.

8. An evacuated high-voltage acceleration tube for the acceleration of particles to high energies comprising a multiplicity'bf. metallic ring-like electrode members and alternating insulating ring-like members constituting the insulating envelope thereof, the said tube having at its respective ends cathode and anodeassemblies', the said 5 tube, for the purpose of increasing the voltage and voltage gradient which can be applied alongthe insulating envelope thereof for the progressive-acceleration of charged particles to high energies, having the axial holes of said metallic ring-like electrode members progressively in creased in diameter from a smallest value at the cathode end of the tube to a larger value near the anode end thereof; 1

9. An evacuated high-voltage acceleration tube for the acceleration of particles to high energies comprising a multiplicity of metallic ring-like electrode members and alternating insulating ring-like members constituting the insulating envelope thereof, the said tube having at its respective ends cathode and anode assemblies, the said tube, for the purpose of increasing the voltage and voltage gradient which can be applied along the insulating envelope thereof for the progres sive' acceleration or charged particles to high energies, having the axial holes differentiated among themselves by reason of a gradual increase in size thereof from thecathode end to the anod end of the-said tube.

10. An evacuated, multiple electrode, accelera tion' tube for the acceleration of electron's or posi f tive ions to high energies, comprising a multiplicity of alternating insulation rings and metallic electrode disks only, bonded directly to each other throughout the tube, the diameters of the axial holes of the insulation rings beinguniioi'in throughout the tube, the said tube having a can: ode assembly and an anode assembly bonded'di rectly at opposite ends to the final'insulation'f rings at said ends, the said electrode disks T40 each provided with an axial holetherethrough for the passage of charged particles the areasorf diameters of said axial holes offthe 'said elec trode disks only, being varied with respect to each other. V r

11. A cylindrical, evacuated, multiple electrode,- tube for the acceleration of electrons or positive ions to high energies, comprising'a"multiplicity"= of insulation rings all of the same'exter'naldia eter and internal diameter, and metallic elecj trode disks thinner than said insulatior'i ringsf 12. and.alternatingwith them and bonded directly to them throughout the said tube, the-outer edges of said insulation rings and electrode disks being substantially co-terminous throughout the length of the said cylindrical acceleration tube, each of the said electrode disks'being provided with an; axial hole therethrough for the passage of charged particles, the areas or diameters of the said axial, holes of the electrode disks being varied with respect to each other, the said cylindrical acceleration tube having a cathode assembly and an anodeas'sembly respectively bonded to the ter-- minal insulation rings at the opposite 'ends of the said cylindrical acceleration tube.

'12. A cylindrical, evacuated, multiple electrode,

tube for the acceleration of electrons or positive ions'to high energies, comprising a multiplicity of insulation rings all of the same external diameter'and metallic electrode disks alternating with them-and bonded directly to them throughout the l said tube, the outer-edges ofthe said insulation rings and electrode disks being substantially coterminous throughout the length of the said cylindricalacceleration tube, each of the'said electrode disks being provided with an axial hole, therethrough for the passage of, chargedjpar; ticles, the areasor diameters of the said axial holes of the electrode disks being varied with respect to each other, the said cylindrical acceloration tube having a cathode assembly and an 'anode assembly respectively bonded to the ter'- minal insulation rings at the opposite ends of thesai'd cylindricalaccelerationtube.

l 1 JOHN G. TRUMP. I 1

ROBERT W QL OUDL REFERENCES CITED The following references are of record inv thev file cums patent: I e

-: -'-.-UNITED STATES PATENTS Number Name 7 Date 1,981,537 Allibone Nov. 20, 1 934 2,145, 72? Lloyd, Jr Jan. 31, 1939 2,156,813 Kautz May 2,1939

' 2,182,185 Trump Dec. 5, 1939 2,227,051 Wiencke Dec. 31, 1940 2,336,774 Brackney'et al Dec. 14, 1943 2,376,439 Machlett et a1 May'22, 1945 2,420,560 Ramo May 13, 1947 Trump et al. 'Jan. 25, 1949 

